Patch "x86/bhi: Enumerate Branch History Injection (BHI) bug" has been added to the 6.1-stable tree

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This is a note to let you know that I've just added the patch titled

    x86/bhi: Enumerate Branch History Injection (BHI) bug

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     x86-bhi-enumerate-branch-history-injection-bhi-bug.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From 71e322ae7bba849c5eec50ad8e599d03bc66bcc9 Mon Sep 17 00:00:00 2001
From: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>
Date: Mon, 11 Mar 2024 08:57:03 -0700
Subject: x86/bhi: Enumerate Branch History Injection (BHI) bug

From: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>

commit be482ff9500999f56093738f9219bbabc729d163 upstream.

Mitigation for BHI is selected based on the bug enumeration. Add bits
needed to enumerate BHI bug.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>
Signed-off-by: Daniel Sneddon <daniel.sneddon@xxxxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx>
Reviewed-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Daniel Sneddon <daniel.sneddon@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/x86/include/asm/cpufeatures.h |    1 +
 arch/x86/include/asm/msr-index.h   |    4 ++++
 arch/x86/kernel/cpu/common.c       |   24 ++++++++++++++++--------
 3 files changed, 21 insertions(+), 8 deletions(-)

--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -489,4 +489,5 @@
 #define X86_BUG_SRSO			X86_BUG(1*32 + 0) /* AMD SRSO bug */
 #define X86_BUG_DIV0			X86_BUG(1*32 + 1) /* AMD DIV0 speculation bug */
 #define X86_BUG_RFDS			X86_BUG(1*32 + 2) /* CPU is vulnerable to Register File Data Sampling */
+#define X86_BUG_BHI			X86_BUG(1*32 + 3) /* CPU is affected by Branch History Injection */
 #endif /* _ASM_X86_CPUFEATURES_H */
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -160,6 +160,10 @@
 						 * are restricted to targets in
 						 * kernel.
 						 */
+#define ARCH_CAP_BHI_NO			BIT(20)	/*
+						 * CPU is not affected by Branch
+						 * History Injection.
+						 */
 #define ARCH_CAP_PBRSB_NO		BIT(24)	/*
 						 * Not susceptible to Post-Barrier
 						 * Return Stack Buffer Predictions.
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1144,6 +1144,7 @@ static void identify_cpu_without_cpuid(s
 #define NO_SPECTRE_V2		BIT(8)
 #define NO_MMIO			BIT(9)
 #define NO_EIBRS_PBRSB		BIT(10)
+#define NO_BHI			BIT(11)
 
 #define VULNWL(vendor, family, model, whitelist)	\
 	X86_MATCH_VENDOR_FAM_MODEL(vendor, family, model, whitelist)
@@ -1206,18 +1207,18 @@ static const __initconst struct x86_cpu_
 	VULNWL_INTEL(ATOM_TREMONT_D,		NO_ITLB_MULTIHIT | NO_EIBRS_PBRSB),
 
 	/* AMD Family 0xf - 0x12 */
-	VULNWL_AMD(0x0f,	NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO),
-	VULNWL_AMD(0x10,	NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO),
-	VULNWL_AMD(0x11,	NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO),
-	VULNWL_AMD(0x12,	NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO),
+	VULNWL_AMD(0x0f,	NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO | NO_BHI),
+	VULNWL_AMD(0x10,	NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO | NO_BHI),
+	VULNWL_AMD(0x11,	NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO | NO_BHI),
+	VULNWL_AMD(0x12,	NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO | NO_BHI),
 
 	/* FAMILY_ANY must be last, otherwise 0x0f - 0x12 matches won't work */
-	VULNWL_AMD(X86_FAMILY_ANY,	NO_MELTDOWN | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO | NO_EIBRS_PBRSB),
-	VULNWL_HYGON(X86_FAMILY_ANY,	NO_MELTDOWN | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO | NO_EIBRS_PBRSB),
+	VULNWL_AMD(X86_FAMILY_ANY,	NO_MELTDOWN | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO | NO_EIBRS_PBRSB | NO_BHI),
+	VULNWL_HYGON(X86_FAMILY_ANY,	NO_MELTDOWN | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO | NO_EIBRS_PBRSB | NO_BHI),
 
 	/* Zhaoxin Family 7 */
-	VULNWL(CENTAUR,	7, X86_MODEL_ANY,	NO_SPECTRE_V2 | NO_SWAPGS | NO_MMIO),
-	VULNWL(ZHAOXIN,	7, X86_MODEL_ANY,	NO_SPECTRE_V2 | NO_SWAPGS | NO_MMIO),
+	VULNWL(CENTAUR,	7, X86_MODEL_ANY,	NO_SPECTRE_V2 | NO_SWAPGS | NO_MMIO | NO_BHI),
+	VULNWL(ZHAOXIN,	7, X86_MODEL_ANY,	NO_SPECTRE_V2 | NO_SWAPGS | NO_MMIO | NO_BHI),
 	{}
 };
 
@@ -1454,6 +1455,13 @@ static void __init cpu_set_bug_bits(stru
 	if (vulnerable_to_rfds(ia32_cap))
 		setup_force_cpu_bug(X86_BUG_RFDS);
 
+	/* When virtualized, eIBRS could be hidden, assume vulnerable */
+	if (!(ia32_cap & ARCH_CAP_BHI_NO) &&
+	    !cpu_matches(cpu_vuln_whitelist, NO_BHI) &&
+	    (boot_cpu_has(X86_FEATURE_IBRS_ENHANCED) ||
+	     boot_cpu_has(X86_FEATURE_HYPERVISOR)))
+		setup_force_cpu_bug(X86_BUG_BHI);
+
 	if (cpu_matches(cpu_vuln_whitelist, NO_MELTDOWN))
 		return;
 


Patches currently in stable-queue which might be from pawan.kumar.gupta@xxxxxxxxxxxxxxx are

queue-6.1/x86-bhi-define-spec_ctrl_bhi_dis_s.patch
queue-6.1/x86-bhi-add-support-for-clearing-branch-history-at-syscall-entry.patch
queue-6.1/x86-bhi-mitigate-kvm-by-default.patch
queue-6.1/x86-bhi-enumerate-branch-history-injection-bhi-bug.patch
queue-6.1/x86-bhi-add-bhi-mitigation-knob.patch
queue-6.1/kvm-x86-add-bhi_no.patch




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